KRAKOW, Poland (AP) - NATO defense ministers meet Friday to discuss reforms to the alliance to help it meet modern threats, as well as the ambitions of Georgia and Ukraine, whose membership aspirations have deeply added to tensions with Russia.

Secretary-General Jaap de Hoop Scheffer has been calling for a new "strategic concept" that would help NATO face 21st century dangers like terrorism, climate change and cyber attacks, a topic on the agenda as ministers gathered for their second and final day of a meeting in Krakow.

On Thursday, U.S. Defense Secretary Robert Gates addressed issues at the core of recent tensions between Washington and Moscow - and the Obama administration’s attempts to improve ties as it seeks greater Russian support for its mission in Afghanistan.

Gates played down Kyrgyzstan’s decision to kick the U.S. off the strategic Manas air base it depends on to supply troops in Afghanistan, a decision Washington believes Moscow has orchestrated. Gates said the U.S. would be willing to pay higher rent - within limits - but said the base was ultimately replaceable.

However, he also said he was skeptical of Russia’s claims to have played no role in Kyrgyzstan’s decision.

Gates also said the Obama administration needed more time to decide whether to go ahead with the previous administration’s plans to build missile defense installations in the Czech Republic and Poland - a program that soured relations with Russia.

Poland’s defense chief had pressed Gates for an answer amid speculation that President Barack Obama could walk away from the deal.

Obama’s administration hasn’t said much about the program, which was a darling of Bush defense advisers. NATO is on record supporting the concept, and some decision is likely before NATO heads of state meet in April.

The defense ministers’ meeting was dominated Thursday by the worsening war in Afghanistan, and the U.S. request for more allied help. Obama approved 17,000 new U.S. forces for Afghanistan this week, and Gates was asking for emergency troops to help protect Afghan civilians from militant violence before national elections this summer.

De Hoop Scheffer acknowledged that the fight against a resurgent Taliban was not succeeding and said failure was not an option. Still, alliance members made no new public pledges of support for the Afghan war.

The 26 defense ministers are scheduled to wrap up the two-day event following talks with their counterparts from Ukraine and Georgia.

Both former Soviet nations have angered Russia by courting the U.S. and by pushing for NATO membership.

At a summit in Romania last year, NATO leaders decided to offer the two governments a so-called "membership action plan" to prepare them for alliance membership despite Russia’s opposition.

Faced with opposition from Russia, NATO has since backed away from establishing a plan for Ukraine and George to move toward entry into the Western military alliance for the former-Soviet nations.

"At the moment I don’t see the conditions for, for example, launching the membership action plan" for Ukraine and Georgia, German Defense Minister Franz Josef Jung said as he headed into Friday’s meetings.